Drive control unit for a power tool

ABSTRACT

Fastener setting power tool having a one-way brake between a housing and a sleeve concentrically supported for rotation within the housing, and a drive control member operable for selectively activating the brake to limit rotation in one angular direction to a preselected displacement.

nited States Patent. [1 1- Whale, J 1'.

1451' Apr. 16, 1974 DRIVE CONTROL UNIT FOR A POWER TOOL Inventor: Clarence F. Whale, Jr., Mayfield Heights, Ohio The Stanley Works, New Britain, Conn.

Filed: Apr. 14, 1972 I Appl. No.: 244,163

Assignees U.S. c1..'. 81/524 R, 144/32, 173/123, 29/240 Int. Cl. B25b 21/00 Field of Search s1/524'R, 52.4 52.41MB, 81/54;'144/32; 192/8 R, 8 c,41s;173/123;

I References Cited UNITED STATES PATENTS 8/1959 Meier 1 ill/52.4 R

3,320,835 5/1967' Flory et a1. 81/54 Primary Examiner-James L. Jones, Jr. Attorney, Agent, or Fi'rmPrutzman, Hayes, Kalb &

[57] ABSTRACT Fastener setting power tool having a one-way brake between a housing and a sleeve concentrically supported for rotation within the housing, and a drive control member operable for selectively activating the brake to limit rotation in one angular direction to a preselected displacement.

8 Clalms, 2 Drawing Flgures DRIVE CONTROL UNIT FOR A POWER TOOL This invention generally relates to fluid operated rotary power tools operable in opposite angular directions for fastener setting operations and particularly concerns a drive control unit which precisely limits angular displacement of such a tool in a selected direction of rotation.

Conventional devices which have been used with rotary power tools to effect a preselected backout after setting a fastener, such as an electrical terminal screw, e.g., to a fixture, have not been found to be completely satisfactory in withdrawing the fastener a desired extent for a subsequent operation such as attachment of an electrical lead to the terminal screw. The fasteners frequently have been completely withdrawn from the fixture during backout and, in other instances, have not been backed out a sufficient amount to permit the next operation to be immediately completed. Accordingly, a primary object of this invention is to provide a significantly simplified mechanical drive control unit which can be bodily incorporated in a rotary power tool or can be used as an accessory or attachment to such a tool for effecting a precisely controlled backout.

Another object of this invention is to provide a new and improved drive control unit of the type described which is of a compact rugged construction quick and easy to manufacture and assemble and which has a minimum number of parts for dependable service over an extensive period of time.

A further object of this invention is to provide anew and improved power tool particularly suited to limit backout of a threaded fastener to a preselected number of revolutions after the fastener is first tightened by the tool to a predetermined torque.

Otherobjects will be in part obvious and in partpointed out in more detail hereinafter. 1

A better understanding of the objects, advantages, features, properties and relationships of the invention will be obtained from the following detailed description and accompanying .drawing which sets forth an illustrative embodiment and is indicative of the way in which the principle of this invention is employed.

In the drawing:

FIG. 1 is a side view, partly in section and partly broken away, showing a part of apower tool incorporating this invention; and

FIG. 2 is a fragmentary isometric view, showing a he lical ball groove formedin a drive shaft of the power tool of FIG; 1. v

Referring now to the drawing in detail, a power tool 10 is shown havinga motor 12 which in the illustrated embodiment is an air motor which will be understood to be connected to a suitable source of air pressure, not shown, for rotating vanes l4'of a rotor 16. Rotor 16 is drivingly connected through conventional gearing 18 to a spindle 20 supported for rotation by suitable bearings such as all While it will beunderstood that this invention may be used in a variety of different power tools, in the specificallyillustrated embodiment, the air tool 10 is a stall type tool shown having a screwdriver bit 24 secured within a bit holder 26 coaxially mounted-at an output end of a drive shaft 28drivingly connected through a splined connection to the spindle 20. Suitable conventional controls, not shown, are provided to selectively drive the air motor 12 in either of two opposite angular directions. Clockwise rotation of the bit holder 26 as indicated by the arrow shown in broken lines at 30 will be assumed to normally tighten a fastener. Counterclockwise rotation of the bit holder 26 as shown by the full line arrow at 32 will be assumed to normally loosen or release a tightened fastener.

To control fastener backout in a counterclockwise direction, e.g., after a fastener has been first driven home in a clockwise direction to a desired torque, the tool 10 of this invention includes a new and improved drive unit 34 operatively mounted between the drive shaft 28 and surrounding housing 36 for backing out a tightened fastener a specified number of turns.

More specifically, the drive unit 34 includes a sleeve 38 supported for rotation on thrust roller bearings 40 mounted within the housing 36 with the sleeve 38 coaxially surrounding the drive shaft 28 in concentric relation to the spindle 20 and housing 36. Thrust roller bearings 40 are operatively secured in assembly with the housing 36 for bearing engagement with a radial flange 42 on the sleeve 38 by a bushing 44 threadably fixed at the front of the housing 36 to surround the drive sleeve 28, and a collar 46 is threadably secured on a free end extension of the sleeve 38. To prevent passage of particulate material such as dust and other undesired matter along thesleeve 38, suitable seals of conventional construction are shown fixed at 48 and 50 about the drive shaft 28 and the sleeve 38 by the collar 46 and bushing 44 respectively.

To precisely control the number of turns of the drive shaft 28 in a fastener releasing or counterclockwise direction, a helical ball groove 52 is formed in an intermediate portion of the drive shaft 28 and an axially extending slot 54 is machined in the inside wall of the surrounding sleeve 38. Operatively received within the groove 52 and the slot 54 is a drive control member or ball 56. The ball 56 is mounted for reciprocable movement relative to the sleeve 38 between first and second operating positions respectively at the front and rear (or the left and right hand) ends of the axial slot 54 as viewed in FIG. I.

In the specifically illustrated embodiment, the collar 46 serves as a closure at the front of the axial slot 54 in the sleeve 38, and the helical groove 52 in the drive shaft 28 is shown having a preselected pitch and lead such that one revolution of the drive shaft 28 moves the ball 56 between its first and second operating positions at opposite terminal ends of the axial slot 54.

As best seen in FIG. 2, opposite ends of the helical groove 52 formed in the drive shaft 28 terminate in shoulders 58 and 60 facing in opposite angular directions for registration with the slot 54 at its opposite ends respectively. Assuming the ball 56 is in its first or forward operatingposition and the tool 10 is activated to rotate drive shaft 28 clockwise, the ball 56 is driven in the groove 52 and traverses axially rearwardly along theslot 54 of the sleeve 38 from the forward operating cifically illustrated embodiment such that ball 56 will be driven from its rear operating position to its forward operating position wherein it engages shoulder 60 of the drive shaft 28 and locks sleeve 38 to the drive shaft 28.

Once locked, further rotation of the drive shaft 28 is virtually eliminated by the provision of a one-way brake which in the illustrated embodiment is shown in the form of a helical spring 64 coiled about a rear shank portion of the sleeve 38 with a radially projecting tang 66 of the spring 64 secured to the housing 36.

By virtue of such a one-way brake, unrestricted rotation of the drive shaft 28 is permitted in a clockwise direction during which time the coils of the spring 64 engaging the sleeve 38 have a tendency to unwrap. Such action is accommodated by the provision of limited spacing between the outer surfaces of the spring coils and the surrounding inside wall 68 of the housing 36. However, as the drive shaft 28 is driven in a counterclockwise direction and ball 56 is moved from its rear operating position into engagement with shoulder 60 in the forward operating position, frictional engagement between the spring 64 and the sleeve 38, which is then locked by ball 56 to drive shaft 28, serves to almost instantaneously arrest the sleeve 38 as the spring 64 contracts radially inwardly about the sleeve 38 to secure it to the housing 36 and terminate the operating cycle by stalling the air tool.

While the helical groove 52 extends through one revolution along the length of the axial slot 54 and while the shoulders 58 and 60 respectively terminate adjacent the opposite ends of the axial slot 54 in general alignment with the slot 54, the above described construction is exemplary only and may be suitably moditied to provide a variable number of turns during backout" depending on the length of the axial slot 54 and the pitch and lead of the helical groove 52 to vary the extent to which a fastener is loosened in accordance with different demands for different applications. Moreover, other devices may be used, for example, to effect the one-way braking action other than the illustrative spring arrangement. However, a power tool embodying the principle of this invention will provide a compact, rugged unit having a minimum number of operating components in an assembly which not only is quick and easy to manufacture but is also relatively free of maintenance requirements for dependable and efficient service over an extended period of time for limiting fastener backout to a precisely controlled angular amount.

As will be apparent to persons skilled in the art, various modifications, adaptations and variations of the foregoing specific disclosure can be made without departing from the teachings of this invention.

1 claim:

lfA power tool comprising a housing, a rotary drive supported within the housing, a drive motor connected for selectively rotating the rotary drive in opposite angular directions, and a driving connection between the housing and the rotary drive positively locking the rotary drive against movement relative to the housing in one angular direction in response to the drive motor moving the rotarydrive from a starting position through a predetermined angular displacement in said one angular direction while permitting unrestricted rotary movement of the rotary drive relative to the housing in the opposite angular direction, the driving connection including a sleeve coaxially supported for rotation within the housing between the housing and the rotary drive, a one-way brake between the sleeve and the housing, and a drive control member received between the sleeve and the rotary drive for reciprocable linear movement parallel to the rotational axis of the rotary drive for selectively operating the one-way brake responsive to movement of the rotary drive through said predetermined angular displacement in said one angular direction from a starting position.

2. The power tool of claim 1 wherein the drive motor is an air motor having a rotor supported within the housing and drivingly connected to the rotary drive, and wherein the driving connection causes the air motor to stall when the driving connection locks the rotary drive after it is rotated said predetermined angular displacement in said one angular direction from said starting position.

3. A drive control unit attachable to a power tool having a fluid operated motor and comprising a rotary drive, a generally cylindrical housing for the rotary drive, a rotatable sleeve coaxially supported at least in part within the housing between the housing and the rotary drive, a selectively operable one-way brake between the sleeve and the housing, and a drive control member mounted between the sleeve and the rotary drive for reciprocable linear movement parallel to the rotational axis of the rotary drive, the drive control member being linearly movable between first and second operating positions as determined by the direction of rotation of the rotary drive for selectively activating and deactivating the one-way brake, the drive control member positively locking the rotary drive against movement relative to the sleeve in one angular direction in response to the drive control member being positioned in said first operating position for activating the one-way brake and limiting angular movement of the rotary drive to a predetermined angular displacement from a starting position and the drive control member in said second operating position drivingly connecting the sleeve to the rotary drive for unrestricted movement thereof in unison in said opposite angular direction.

4. The drive control unit of claim 3 wherein the drive control member when moved from its second to its first operating positions is operable for temporarily unlocking the sleeve from the rotary drive for rotation of the rotary drive through said predetermined angular displacement, the drive control member activating the one-way brake when the drive control member is positioned in its first operating position to lock the rotary drive and sleeve to the housing for stalling the fluid motor of the tool.

5. The drive control unit of claim 4 wherein the drive control member when moved from its first to second operating positions is operable for temporarily unlocking the sleeve relative to the rotary drive and deactivating the one-way brake for unrestricted rotation of the rotary drive and drive sleeve in unison through a driving connection effected by the drive control member in its second operating position.

6. A drive control unit attachable to a power tool having a fluid operated motor and comprising a rotary drive, a generally cylindrical housing for the rotary drive, a rotatable sleeve coaxially supported within the housing between the housing and the rotary drive, a one-way brake between the sleeve and the housing, and

a drive control device for selectively connecting the rotary drive to the sleeve including a drive control member for operating the one-way brake responsive to movement of the rotary drive a predetermined angular displacement in one angular direction from a starting position,the drive control device including a helical groove formed in the rotary drive and .a longitudinally extending slot formed in an inside wall of the sleeve surrounding the rotary drive, the slot and the helical groove being of generally corresponding axial length and having complementary terminal portions registrable with one another for establishing first and second operating positions of the drive control member, the drive control member comprising a ball disposed within the helical groove of the rotary drive and the longitudinally extending slot of the sleeve for movement along the sleeve between said first and second operating positions at opposite ends of its longitudinally extending slot.

7. The drive control unit of claim 3 wherein the oneway brake comprises a helical spring coiled about the sleeve, the spring having one end connected to the housing with its coils in engagement with the sleeve and in adjacent spaced relation to the surrounding housing for expansion radially of the sleeve responsive to rota tion of the sleeve in said opposite angular direction and operable to effect radial contraction of the coils about the sleeve responsive to rotation thereof in said one angular direction.

8. The drive control unit of claim 6 wherein the helical groove has a preselected lead and pitch which with said axial length of the groove and the slot jointly cooperate to define said predetermined angular displacement of the rotary drive in said one angular direction from a starting position, the one-way brake being effective to substantially preclude further rotation of the rotary drive beyond said predetermined angular displacement upon the drive control ball being moved from its second operating position into its first operating position. 

1. A power tool comprising a housing, a rotary drive supported within the housing, a drive motor connected for selectively rotating the rotary drive in opposite angular directions, and a driving connection between the housing and the rotary drive positively locking the rotary drive against movement relative to the housing in one angular direction in response to the drive motor moving the rotary drive from a starting position through a predetermined angular displacement in said one angular direction while permitting unrestricted rotary movement of the rotary drive relative to the housing in the opposite angular direction, the driving connection including a sleeve coaxially supported for rotation within the housing between the housing and the rotary drive, a one-way brake between the sleeve and the housing, and a drive control member received between the sleeve and the rotary drive for reciprocable linear movement parallel to the rotational axis of the rotary drive for selectively operating the one-way brake responsive to movement of the rotary drive through said predetermined angular displacement in said one angular direction from a starting position.
 2. The power tool of claim 1 wherein the drive motor is an air motor having a rotor supported within the housing and drivingly connected to the rotary drive, and wherein the driving connection causes the air motor to stall when the driving connection locks the rotary drive after it is rotated said predetermined angular displacement in said one Angular direction from said starting position.
 3. A drive control unit attachable to a power tool having a fluid operated motor and comprising a rotary drive, a generally cylindrical housing for the rotary drive, a rotatable sleeve coaxially supported at least in part within the housing between the housing and the rotary drive, a selectively operable one-way brake between the sleeve and the housing, and a drive control member mounted between the sleeve and the rotary drive for reciprocable linear movement parallel to the rotational axis of the rotary drive, the drive control member being linearly movable between first and second operating positions as determined by the direction of rotation of the rotary drive for selectively activating and deactivating the one-way brake, the drive control member positively locking the rotary drive against movement relative to the sleeve in one angular direction in response to the drive control member being positioned in said first operating position for activating the one-way brake and limiting angular movement of the rotary drive to a predetermined angular displacement from a starting position and the drive control member in said second operating position drivingly connecting the sleeve to the rotary drive for unrestricted movement thereof in unison in said opposite angular direction.
 4. The drive control unit of claim 3 wherein the drive control member when moved from its second to its first operating positions is operable for temporarily unlocking the sleeve from the rotary drive for rotation of the rotary drive through said predetermined angular displacement, the drive control member activating the one-way brake when the drive control member is positioned in its first operating position to lock the rotary drive and sleeve to the housing for stalling the fluid motor of the tool.
 5. The drive control unit of claim 4 wherein the drive control member when moved from its first to second operating positions is operable for temporarily unlocking the sleeve relative to the rotary drive and deactivating the one-way brake for unrestricted rotation of the rotary drive and drive sleeve in unison through a driving connection effected by the drive control member in its second operating position.
 6. A drive control unit attachable to a power tool having a fluid operated motor and comprising a rotary drive, a generally cylindrical housing for the rotary drive, a rotatable sleeve coaxially supported within the housing between the housing and the rotary drive, a one-way brake between the sleeve and the housing, and a drive control device for selectively connecting the rotary drive to the sleeve including a drive control member for operating the one-way brake responsive to movement of the rotary drive a predetermined angular displacement in one angular direction from a starting position, the drive control device including a helical groove formed in the rotary drive and a longitudinally extending slot formed in an inside wall of the sleeve surrounding the rotary drive, the slot and the helical groove being of generally corresponding axial length and having complementary terminal portions registrable with one another for establishing first and second operating positions of the drive control member, the drive control member comprising a ball disposed within the helical groove of the rotary drive and the longitudinally extending slot of the sleeve for movement along the sleeve between said first and second operating positions at opposite ends of its longitudinally extending slot.
 7. The drive control unit of claim 3 wherein the one-way brake comprises a helical spring coiled about the sleeve, the spring having one end connected to the housing with its coils in engagement with the sleeve and in adjacent spaced relation to the surrounding housing for expansion radially of the sleeve responsive to rotation of the sleeve in said opposite angular direction and operable to effect radial contraction of the coils about the sleeve responsive to rotation Thereof in said one angular direction.
 8. The drive control unit of claim 6 wherein the helical groove has a preselected lead and pitch which with said axial length of the groove and the slot jointly cooperate to define said predetermined angular displacement of the rotary drive in said one angular direction from a starting position, the one-way brake being effective to substantially preclude further rotation of the rotary drive beyond said predetermined angular displacement upon the drive control ball being moved from its second operating position into its first operating position. 